fix: unify background color for "No more data" indicator

- Add Color.itemBg background to LoadmoreIndicatorView to match content area
- Add Color.itemBg background to ScrollView in UpdatableView for consistent
  background color throughout the entire scrollable area

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: graycreate

V2er/View/Widget/Updatable/LoadmoreIndicatorView.swift

@@ -30,6 +30,8 @@ struct LoadmoreIndicatorView: View {
             }
         }
         .padding()
+        .greedyWidth()
+        .background(Color.itemBg)
     }
 }
 

V2er/View/Widget/Updatable/UpdatableView.swift

@@ -76,6 +76,7 @@ struct UpdatableView<Content: View>: View {
                     }
                 }
             }
+            .background(Color.itemBg)
             .onChange(of: state.scrollToTop) { scrollToTop in
                 guard scrollToTop != 0 else { return }
                 withAnimation {